Look on your receiver tag for your maximums when weight carrying and using weight distribution. I know Ford upgraded the receiver since 2005 - Using mine as an example, it was rated for 500 lbs tongue weight and 5000 lbs trailer weight when weight carrying and 1250 lbs tongue weight and 12,500 lbs trailer weight when using weight distribution.
According to the 2015 towing guide, yours is rated 850 lbs tongue with 8500 lbs trailer without WDH and 1400 lbs tongue with 14,000 lbs trailer with WDH.
http://www.ford.com/resources/ford/general/pdf/towingguides/15RV&TT_Ford_SuperDtyPU_r1_Jan12.pdf
